Influence of electrodeposition conditions on the microstructure and corrosion resistance of Zn–Ni alloy coatings from a deep eutectic solvent

• Zn–Ni alloy films from a choline chloride–urea eutectic-based ionic liquid
• Electrodeposition parameters (temperature, voltage and bath composition) are studied.
• Dense, smooth and fine structure with optimum Zn content for barrier corrosion protection

The collective influence of crucial electrodeposition parameters (temperature, deposition voltage and bath composition) on the properties of Zn–Ni films electrodeposited in a choline chloride–urea eutectic-based ionic liquid was investigated. The microstructures, chemical compositions, phase structures and corrosion behaviors of electrodeposited films were analyzed using scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction and linear cyclic voltammetry, respectively. The surface morphologies and chemical compositions of the films were strongly dependent on the electrodeposition parameters. It was found that the amounts of nickel in the Zn–Ni alloy films were significantly higher than that present in the electrolytes and was always above 50%, indicating normal codeposition mechanism. Electrodeposition of high Zn content alloy is favorable at high electrodeposition voltages, high temperatures and high Zn (II)/Ni (II) ratios. Electrochemical measurements shows that under the conditions considered, the Zn–Ni film from 0.45 M Zn (II)–0.05 M Ni (II) deposited at 55 °C and 0.8 V exhibits the highest barrier corrosion resistance compared with the other films and this was attributed to a dense, smooth and crack free morphology with optimum Zn content.